Circuit breaker



Apnl 27, 1954 1 w. DYER 2,677,025

CIRCUIT BREAKER Filed May 2, 1952 2 Sheets-Sheet 1 INVENTOR Lloyd W. Dyer. BY MMM ATTORNEY HHHUUU. NMHDU HHHDU HHHHHE s z 7///////-/////7/M wm. m ow. MM

April 27, 1954 L. w. DYER 2,677,025

CIRCUIT BREAKER Lloyd W. Dyer. MM. QM im ATTORNEY 3 pivoted ends of legs |51 of the switch arm |31 across to the left of the line of action of the operating spring |39 which then biases the switch arm to the open position and causes movement of the switch arm to open position with a snap action.

The contacts are manually closed by reverse movement of the handle. Counterclockwise movement of the handle |46 from the open position to the closed position moves the upper pivoted ends of legs |51 of the switch arm |31 across to the right of the line of action of the spring |39 which thereupon acts to close the contacts with a snap action.

An arc extinguisher |60 is provided to quickly extinguish the arc drawn when the circuit is interrupted. The arc extinguisher may be of any suitable type but preferably comprises a stack of spaced slotted plates of magnetic material.

The circuit breaker is adapted to be tripped open instantaneously in response to overload currents above a predetermined value, or in response to a short circuit current, and after a time delay on lesser overload currents, by means of the trip device |2 Operation of the trip device |2| releases the carrier |33 whereupon the operating spring |36 moves the carrier |33 clockwise moving the line of action of the spring |39 across to the right of the pivot of the switch arm |31. Thereafter the spring |39 acts to move the switch arm to open position with a snap action. The movement of the carrier is arrested by engagement with a projection I6! of the housing The trip device |2| comprises a bimetallic thermal element |65 connected by means of the iiexible conductor |59 to the switch arm |31 and an electromagnet including a magnetic member or armature |63 mounted on the thermal or bimetal element |45 and an H-shaped magnetic member or magnet yoke |65 having the long ends |64 mounted in a recess |66 in the side wall of the housing and in a companion recess |68 in the cover ||3 (Fig. 3) for limited movement relative to the magnetic member |63. The conducting strip |29 is secured to the end wall of the casing by means of a screw |1| and the bimetal element |65 is rigidly secured by suitable means such as welding to an offset portion of the upper inner end of the conducting strip |29.

The magnetic member |63 is rigidly secured to and surrounds three sides of the thermal member |45. The magnetic member |63 is secured to the thermal or bimetal element |65 by means of a rivet |13, which is formed lrom enamel or plastic coated wire, and also serves to secure a latch element |61 to the bimetal element. The latch |61 normally engages and releasably restrains the carrier |33 in operative position. The holding force is applied to the bimetal |45 in tension and does not stress the bimetal with a bending force. The reason for insulating the latch |61 from the current carrying bimetal |45 is to prevent the drawing of an arc between the latch |61 and the end of the releasable member |33 when they separate on tripping. While the flexible conductor |59 is provided to carry the main flow of current from the bimetal to the moving contact, there would also be a parallel current path, if the latch were not insulated, from the latch to the releasable member and through the spring |39 to the contact actuating arm |31 and the `contact ||1. With such a parallel path, there would be a small arc drawn between the end ofthe member 33 transfer ofthe current flowing through the par- 4 Y l allel path to the main path through conductor |59. By eliminating the drawing of an arc at the latch surfaces, burning or roughening of these surfaces is avoided so that latch friction is maintained constant and the calibration of the breaker does not change with use.

To accomplish this, the latch member |61 is y insulated from the armature |63 and from the bimetal element |45 by thin sheets of insulating material |84 (Fig. 4) inserted between the parts and by means of the enameled shank of the rivet |13 which is formed from a section of wire precoated with a suitable insulating material such as enamel or a vinyl plastic |14. The fact that the rivet |13 is formed from coated or enameled Wire, or is otherwise provided with an enameled or insulated shank, has the advantage that the latch piece |61 need not be accurately positioned relative to the rivet during the assembly of the parts so as to provide clearance between the rivet and the edge of the hole in the latch piece |61, as would be necessary if the shank of the rivet were not covered with insulation.

The magnet yoke |65 is biased by means of a light compression spring |11 toward the armature |63 and against shoulders |19 of the recess |66 in the housing and shoulders |82 of the recess |68 in the cover plate H3 (Fig. 3).

The stop projections |19 and |82 hold the magnet yoke |65 away from the armature |63 a distance greater than the amount of movement that is required to release the end of the trip member |33 from the latch portion |61, so that upon both thermal and magnetic tripping the tripping action takes place before there is any movement of the magnetic member |65 and independently thereof and of the spring |l1. The distance between the projections |19 on member 'lli and the projections |82 on member ||3 is greater than the Width of the bimetal l45 so that the bimetal may move therebetween. Like wise, the distance between the two projections |19 and the distance between the two projections |82 is each greater than the depth of the armaf ture so that the armature can move between the two projections of each pair even though the armature is wider than the bimetal and the distance between projections |19|19 and |82- ||22 on the two members. Thus, the armature and bimetal together form a cross-shaped structure which moves between the four projections on the housing members.l

A spring guide projection |18 is formed on the magnet yoke |65 by any suitable process such as embossing which also provides a recess 83 on the opposite side of the magnet yoke thus providing clearance for the head of the rivet |13 when the armature |53 is attracted against the magnet yoke |65.

With normal rated current owing through the bimetal element |45 the magnetic member |65 is in the position shown in Fig. l. Upon the occurrence of an overload current above the rated current and below a lpredetermined value of, for instance, 1000% of normal rated current, the bimetal element |45 is heated by the current ow therein and deilects toward the right causing the latch |61 to release the carrier 33 whereupon the operating 'mechanism functions in the previously described manner to automatically open the breaker contacts.

Upon the occurrence of a heavy overload current or short circuit current, such for example 'as 1000% or more of normal rated current, the

current flowing through the bimetal element |45 genoss Venergizl-:s T'theelectro-magnetic"meansL @sufficient .amount to"- causevv the magnetic member -f |65 'to instantaneously attract andoperate the-magnetic member |63 thus bending the'bimetal-element andl causing release of the carrier 33 Vand erfectingiinstantaneous opening'of the breaker'contacts.

tBei'ore*the contacts-canbe closed following ein-*automatic opening operation, Eit isfnecessary to "resetf'and relatch the "mechanism- This 'is accomplished" by moving V-the vhandle |49' clockwiseA to* the full openHposition duringwhich movement *the legs `|5il`f the operating lever |351engagefa'pin it! in thecarri'er |33 andmoves the. carrier counterclcckwise about its-V pivoti4 Nearthe-'endfof its counterclockwise movement, the ree'enld ofthe carrier |33 V:wipes'f by the latch le?, slightly lbending the bimetal` element whichfthereafter resumes its normal latching position. The switchfa rm is then moved to closefthelcontacts in the-previously described manner bymovement of the "handle 'counterclockwise to" the' closedposition.

During the time interval between the initiation ofl the' trippingv'action and themechanical-opening of thecontacts andi the' extinguishing of Vthe arc, the excessive current continues to -now through and heat the bimetal, and the vbimetai continues to exan'd lbend beyond the tripping point. element is opposed'by' anysubstantial forcesuoh as by engaging a fixed magnet yoke while the bimetal 4is hot, it 'may `take a permanent set which Ywilbdestroy its calibration. For this reason,and"to `take'care ofthe greater movement f'the 'bimetal atk its outer end, the magnetic member"|65 'isnormally positioned at an'angle toftheibimetal and tolthe movable armature 163;"andthe recesses land. '|53 aremade wider at their lower ends 'topermit movement of at least'thelower end ofthe'magnetyoke in the dire'ctionof thermal bending of the bimetal elenient'ldt vso"that, uponpcntinued'bending, the bimetal haswtofovercomeionly the relative light force 'of the'spring ill, Aitenthe bimetal has cooled,- the'light spring.' VET krestores ythe magnet yoke v|65 toits' normal' position.

'The distance' between each shoulder 9'on one section of the housing'andthe opposite shoulder |82 ontheotherlsefction ||3 `isgreater than r ,the width of the bimetal V|45 sothat the bimetal maybend and move betweenthe shoulders withoutV engaging them. Likewise, the space between theprojecting ends |54ofthe"H-shapedmagnetic member |35 isgreater' than'thewidth oi the bimetal so `thatthe bimetal does not engage thelendsi'li. "These features of construction, together with the recess |33 for'the formed-over end"|.'|3 :of 'the rivet and the movable mounting of the magnetic member '|65 with provision for greater movement at the movable end of the bimetal element, permit a maximum amount of .thermal bending of .the bimetal element, as illus- .tratdin'Fig 5, to a' greater extent'than is likely t6 take` 'placein actual use. rlhis insures'against the "nimetall losingits calibration due to having been. restrained 'against movement when it is .highly` heated,..and"this resultis obtained in a vstructure which is compact and requires a minor" space, it being noted that the magnetic trip structure ts into'the relatively small space .between 'the bimetal '|45 and lconducting strip "|23 and' terminal' |3|.

'Adjusting meanslis rprovided whereby' the vtrip `"device may be adjusted to vary the tripping point Ifsthe thermal-bending of the lbim'etal V'butis' releasably restrained by. meansoithe trip of theL thermal 'tripfm'eans fThe-fdjustingffmeans comprises an adjusting-screw t8 threadedflyengaging at plate or squarefnut Y| 85fdisposed1i linsa recess |81 in- -thei housing llt-anda slotllBYin the cover plateffl |3"'(Fig."3). `The`finner endfof thescrew 8 l 'engages the lupperf end Iof" the' conducting strip |28. An opening? I9 lf'fin the housing provides access'lpermitting the finsertion \f a screw driver toi-turn the screw 1| 8 to thereby adjust Etlhetrip fdevice. A:The opening "l 9 Iemay-be sealed after adjustment to `preventi'tampering@by unauthorized persons.

LA'Referring fnew' to'fFigs.- '8f and?? of the rdrawing. thek circuitlbreaker of this embodiment comprises a casi-ng' including ahousing `-(Fig.'6) andra, cover `I3 "(Fig."`7),""bothfof -m`olde`dv insulating material, stationaryflcontact means- 'l-landi'cooperating movable contact means |f'|, f operating mechanism-indicated generally at i3' and a Ltrip deviceindicatedgenerallyat 2 'The stationary contact 'l 5 is `rigidlysecured on the'inner fend of a 4terminal f conductor 23 which extends outwardly through an'opening in -theadjacent end wall of the housing ||-and 4*has a vvconnecting means atk its outereend. "The movable contact |'1 rigidly mounted on one-end of'a'swit'ch arm 2l pivotailysupported at itsy otherren'ddon apivotf23 molded integral with' theside wallof the housing Il.

The switch yarm Zf-is biased closed-by'a'fcompression spring3| having oneend-v seated-ina 'spring-seatin the base of Ythe housing liand having its other end-engaging a'springseat on the switch'arm. nn operating 1ever'33'pivoted 'on a pivot 35moldedintegralwith'the sidewall of the housing hasacam surface 3l Aon vthe inner-end-thereof adapted, upon clockwise movement Aof the lever 33, to engage a pin-'39 inthe switch arm 27 and-move the switch arm counterclockwise to'an open position'in `which ar recess 4| inthelever 33engages thepin39"to"hold the switch `arm in the kopen position.

The operatinglever 33 'is provided with'a4 handle member 43 extending loutwardly through 'an openingl'itlfl in the-housing'and an integralvarcuate portion lll of the handlesubstantiallyjcloses vthe opening 45 in all positions of the'handle.

The contacts are manuallyv vopenedby clockwise"mmfenienty of kthe handle and the operatingll'ever v33 to "the 01T position during which Ymovement the cani surface'lv acts .on the pin 39 to'move the switchmember 21 to. thek open position further compressing the 'spring 3|. Movement of thehandle 43. and the operating lever 33 counterclockwise to the on position permits the spring 3| to move the switch member 2'! to. close the contacts.

Pivotally mounted on the pin is a releasable member biased in a counterclockwise direction by 'means of a spring 5| having one endseated in a springV seat inthe end wall ofthe housing ||V and-the `other end engaging` a springguide v53 on vthe releasable member 43. The releas'able member '43 is normally biased by the spring"'5| for movementlin a counterclockwise,direction device 2|. Operation vof the tripdevice, which will be hereinafter |describedin detail, vreleases the releasable member 119 whereuponthe s'pring-5|y whiclfiisof considerably greater strength than the spring 3 I., rotates the releasable memberilsharp- `1y counterclockwise.

This movement causes. a camsurfacet onthe releasable member 43 ,to

...engage the pin 39 andmovethe 44switch member"2| tothe open position.

When the switch member 21 is automatically moved to the open position by the releasable member 49, the handle 43 is moved to an intermediate indicating position by means of a leaf spring 51 having one end seated in a recess in the housing II and bearing against the arcuate portion 41 of the handle.

The releasable member 49 is reset and relatched and the contacts closed following an automatie operation by first moving the handle clockwise to the full oir position and then counterclockwise to the on position. When the handle 43 is moved to the off position a surface 59 on the arcuate portion 41 thereof engages and moves the releasable member 49 to its normally restrained position. Counterclockwise movement of the handle 43 then permits the spring 3| to close the contacts.

The trip device 2i comprises a bimetal element 6I having its lower end (Fig. 6) rigidly secured to the inner end of a terminal conductor 63 rigidly supported by means oi a screw B on the end wall of the housing, and having a portion extending out through an opening in the end wall of the housing. A terminal connector 51 is secured to the outer end of the conductor 63. The upper or free end of the bimetal element is connected by means of a flexible conductor 69 to the switch member 21.

A U-shape-d magnetic member or armature 1I surrounds three sides of the bimetal element adjacent the free end thereof. A iiXed magnet yoke 13 is supported in a recess iii in the end wall of the housing il for limited movement relative thereto. The magnet yoke 13 is provided with iianges 11 which engage shoulders 19 on the housing I I to limit the movement of the magnet yoke 13 toward the armature 1I. A light compression spring iiI seated in a spring seat in the end wall of the housing II biases the iixed magi net yoke 13 toward the armature 1I and against the shoulders 'i9 on the housing to provide a normal air gap between the magnet yoke 13 and the armature 1I. The armature 1I also serves as a latch and normally engages a latching portion B3 of the releasable member 49 and releasably restrains the releasable member in operative position as shown.

Means is provided foi` Calibrating the trip device. This means comprises a screw 85 threaded into the terminal conductor 533 at the point where the bimetal element il is mounted thereon. The screw 35 has a round head 81 seated in a recess in the end wall of the housing II. An opening S9 is provided for the insertion of a screw driver to rotate the adjusting screw B5. Turning the screw 855 will cause bending of the conductor 63 and corresponding variation in the position of the bimetal ele xent iii according to the direction in which the screw eil is rotated to thereby vary the tripping point oi the breaker.

Upon the occurrence of a low, persistent overload current below a certain value, for instance, ten times normal rated current, the bimetal element is heated and bends toward the right (Fig. 6) causing release of the releasable member 49. The releasable member causes movement of the switch arm 21 to the open contact position in the manner previously described.

When an overload current above ten times normal or a short circuit current occurs, the electromagnetic trip means is energized and the armature 1 i 'is attracted toward the magnet yoke 13 bending the bimetal element and causing instantaneous release of thereleasable member 49 8 and opening of the contacts. The releasable member 49 is reset and relatched following an automatic opening operation in the previously described manner.

During the time interval between the tripping action and the mechanical opening of the contacts the excessive current continues to iiow through and heat the bimetal, and the bimetal element continues to flex or bend beyond the tripping point. If the thermal bending of the bimetal element is opposed by any substantial force such as by striking a fixed magnet yoke while the bimetal is hot, it will take a permanent set which will destroy its calibration. For this reason the magnet yoke 13 is movable in the direction of thermal bending of the bimetal element 6I so that, upon continued bending, the bimetal element has only to overcome the relatively light force or" the spring 8|. After the bimetal element has cooled and resumed its normal position the spring 8| restores the magnet yoke 13 to its normal position with the anges 11 thereon abutting against the shoulders 19 on the housing I I.

Having described the invention speciiically in accordance with the provisions of the patent statutes, it is to be understood that various changes and modications may be made in the structural details and combination of elements disclosed without departing from some of the essential features of the invention.

I claim as my invention:

l. In a circuit breaker having separable contact means and means releasable to effect separation of said contact means, trip means for efiecting release or said releasable means in respons@ to overload currents comprising a bimetal element, magnetic means including an armature mounted on said bimetal element, said bimetal and armature having a portion for releasing said releasable means, thermal bending of said bimetal element causing release of said releasablg means, a magnetic yoke mounted separate from said bimetal element and supported for limited movement in the direction of thermal bending of said bimetal element to permit maximum bending of said bimetal element Without substantial opposition, relatively light spring means biasing said magnetic yoke to normal position relative to said armature, and said magnetic yoke upon energization of said magnetic means attracting said armature and bending said bimetal element to cause instantaneous release of said releasable means.

2. lin a circuit breaker having separable contact means and means releasable to effect separation of said contact means, trip means for effecting release of said releasable means in respense to overload currents comprising a thermaily responsive element, magnetic means including a rst magnetic member mounted on said thermally responsive element, said iirst magnetic member having a latch surface movable therewith engaging and releasably restraining said releasable means, thermal bending of said thermally responsive member in response to overload currents causing said magnetic member to release said releasable means, a second magnetic member mounted on a fixed support for limited movement in the direction of thermal bending of said thermally responsive element, spring means biasing said second magnetic member Vto a predetermined position to form a predetermined initial air gap with said first magnetic member. said spring means permitting thermal bending 9i;L of: saidLtl'iernialiy:responsive element far; distance greater .than said initial air can' with afminimum of roppDsitionY, and saidy vmagnetic members I-vvhen energizedin responsefto excessive-currents bending saidtherrnally responsivemeans to'efect n. stantaneousreleaseof said releasable means.

3'. Ina circuit ,break'cnhavingrelatively movable. contactxneansy and meansreleasable to1-ef fect opening ofisaid contact.meansfcurrent responsivemeans `for.eifectingrrelease-of said releasable meansin .response tooverload currents comprising a .magnetici yoke mounted, on, a1- .xed

support for limited movement, means. energizing saidniagnetic yoke in response` to.` current y.lovv through said breaker, an armaturemember :move able. toward Y said magnetic yOketo bend :said bimetalelement and Aeffect release/of said :releasable meanslinresponse tofioverload currents,- springimeans biasing.v said .magnetic yoke i to Aapredetermined position, said magnetic yokeY in4 saidpredetermined, posit-ion cooperating with said armature to define a .predetermined -initialmagneticy air gap. and said vspring; means .permitting said. armature torno-vea distancetgreater thansaid vpredetermined initial air gap.:

4. In acircuit breaker,- having relatively: movable :contact :means and ,meansreleasable to efe fect opening of,said A,contact means, vcurrent responsive means foreffectingzrelease oisaid -ree lasabl '.means in response to overload currents comprisingv a. bimetal,y element,Y an: armature mountedron ,andnembracing saidY bimetal element to beenergizedin responser to current flowing through .said bimetal velement,y a magnetic yoke mounted. separate fromzsaid lbimetal element vfor limited movement, means limiting'` movement -f of-` said magnetic yoke toward said armature,vspring meansbiasing said magneticyoke against said. limiting meansto, provideaznormal initial air gap between .said magnetickv yoke and said .farmature,. said. armature fengagingfand'A moving vsaid magnetic yoke upon yexcessive.therrria1,bending of said bimetal element.,

5.In a circuit-breaker having :separable con-V tact L.means and meansreleasablez-to veffect -fseparationfoisaid contact means; a'fbimetalelementl responsive toy toverload currents Y for effecting;y releasel'oif.L saidv releasable,'means;.a- .frst magnetic member.supportedl on-` saidi'bimetal element to be energized by current flowing` ;througl1 said bimetal element; said: rst magnetic member have ing,4 a .portion; -movable'f therevvii'fli-H normally ene gagingf and ,releasablyjf restraining@ said release;

ablemeans;v as second Armignetic i Amernb er; means separate fremf saidbimetalA element v supporting said -second-rnagnetic membervforflimited .move-4 ment, stop lmeanslimitingtheernoifeinent:of said second magneticfmemberutcward .said armature; biasing; means biasing;v said E second; magnetic memberV against said-1 stop;L means .providing a normal air gap;lv said "flrstsmagnetic' memberV ene gagin-g and` movingsaid'secondzlmagnetic ymemev ber upcirthermalA bendi'lngff:oi` saidabimctalg-ele-i ment;

6. In a circuit 1breaker?-havingrfrelatively"mov able.A contacts and means:releasable':y to eiect opening of` said contacts; currentA responsive means;l fory eilieetingl releasefof'f said"y releasable means in responsez to' overload currents: belowpredetermined :value-icomprising azbimetai elef ment,: magnetic Ameansw-for effecting ainstantanee ous 2 release of saidf yreleasable :means 'comprising a-s magnet yoke-.mounted yfor 'limitedy movement; aniarmature amounted, on said ilbimetai element von the l'side thereofnaway from-:,said,:masneti yokenla,

rivet securing saidA armaturey to. said ybimetal. element having ahead on the side of said bimetal element adjacent said magnet yoke, a relatively light spring biasing said magnet `yoketoa predetermined position, said magnet yoke being embossed to form aA clearance recess for said rivet head on one side thereoi-anda-raised portion on the opposite side thereoflforming aI seat for said spring.

'7. A circuit breaker including an open-sided housing `member of moldedk insulating material and a closuremember also of `molded-insulating material mounted on said .openesided housing, relatively movable `contacts, rmeans releasable to eiect opening of saidcontacts, current responsive means for effecting release of said releasable means in response toI certain overload currents comprisinga binietal element, magnetic means forzeiecting release of said releasaole means in response to certain. other overload currents comprising a magnet yoke saidopen-sided housingv memberand saidy closure member each having matching recessesl and surfaces therein for receiving and supporting onefof the.y opposite edges `of said magnet yoke for limited movement, an armatureymounted on said bimetal element and movable toward said magnet yoke upon en-` ergization of ysaid niagneticmeansby saidlother overload: currentsdspring means biasing said magnet yoke to a predetermined positionv to ,form an initial air gap withl said armature,. andlsaid spring means permitting saidfa-rmature .toirinove afcdistance greater than saidinitial airQV gap,...

8.,v A circuitv breaker including anpenfsided housing member or" molded insulatingv` vmaterial and a closure member-alsoof.moldedinsulating material Y mounted Yon said, Y openmsided housing, relatively movable contacts, .means releasable to effect opening of -said :contacts, current Y respon.-

ive means for eiectingfreleasefof,saidireleasable means-ingresponse torcertainoverload. currents e comprising bimetal element, magnetic means. 1 for eiecting release`v oir said,n releasable means'in response. tol certain otherfoverloadcura rents comprising aimagnetyoke,,saidropengsided housingmember `end saidclosnre Jnembervt each having i supportinggmeansifor :receivingoneA side of; l said magnetgyokeeandgthef-fdistance. between thea supporting i means one, the housingy member and the supportinggmeans ori-theclosureiinem-A ber beinggreater:than-, thewidtnofthecbimetal element. to permit thebimetal elementntoimove.v

between .the supporting ineensoongthe .two mem.-. bersasaid;,supporting mean'sipermittingf limited movement:` cigsaid..y magnet;iyokef,A an armature.

mounted; on isaidrbimetanelement :and movable toward; sa-idmagnetf yoke` upon energization 10isaid magnetic means byi said otherfoverload-curfrents, spring means `biasing-said magnet yok'etoal predetermined position tofform, an initial air gap with said armature-,and said spring means..,p.er;. mitting saidarmatureftormovef,aidistancergreater than isaid linitiale-ir :gap-

9: i circuit breaker including' an open-sided housingjfmemberfr of molded; insulating material. and "a closure-member also or molded insulating material mounted on said' opemsided housing;v relativelymovable contacts; means releasable Ato ei'ect openingA of saidcontacts:currentresponi sive meansicr eiectingreiease: of said releasable mean-s v; in respcnsesto.- certainvoyerload currents comprising a bimetal element, magnetic means for effecting release Iof `said-vreleasable :meanszin response-to ,certain ,otheroverloadfvcurrents come prisms :ami-issue;

armature member on the bimetal element of greater width than the bimetal element, said open-sided housing member having a pair of spaced projections for engaging the opposite ends of one side of the H and said closure member having a pair of spaced projections for engaging the opposite ends of the other side of the H, the distano-e between the projections on the two members being greater' than the width of the bimetal element and the space between the projections on each member being greater than the depth of the armature so that the bimetal and armature may move together between the four projections.

l0. A circuit breaker including an open-sided housing member or molded insulating material and a closure member also of molded insulating material mounted on said open-sided housing, relatively movable contacts, means releasable to effect, opening of said contacts, current responsive means for eiiecting release of said releasable means in response to certain overload currents comprising a bimetal element, magnetic means for effecting release of said releasable means in response to certain other overload currents cornprising an H-shaped magnetic member and an armature member on the bimetal element of greater width than the bimetal element, said open-sided housing member having a pair of spaced projections for engaging the opposite ends of one side of the H and said closure member having a pair of spaced projections for engaging the opposite ends of the other side of the H, the distance between the projections on the two members being greater than the width of the bimetal element and the space between the projections on each member being greater than the depth of the armature so that the bimetal and armature may move together between the four projections, and said H-shaped magnetic member being movable by said bimetal and armature only after release of said releasable means.

1l. In a circuit breaker, a housing of insulating material, separable contacts, means releasable to effect separation of said contacts, trip means for effecting release of said releasable means comprising a bimetal element, an armature positioned on one side of said bimetal element and movable to effect release of said releasable means, a magnetic member positioned on the other side of said bimetal element and supported by the housingv of insulating material forA movement in the direction of movement of the bimetal element when heated, said magnetic member being movable by movement of the bimetal element when heated and being supported by the housing at such distancefrom the bimetal element that the magnetic member vis not moved until after the bimetal element has moved a distance suicient to cause release of said releasable means.

12. In a circuit breaker having relatively movable contacts and means releasable to eect opening of said contacts, current responsive means for effecting release of said releasable means in response to overload currents, a latch member normally engaging and holding said releasable member, said latch member being mounted on said current responsive means and insulated therefrom by means including a fastening member passing through said latch member and said current responsive member, and a coating of an insulating composition on the shank of said fastening member. i

13. In a circuit breaker having relatively movable contacts and means releasable to effect opening o'f 4said contacts,"currentresponsive means for effecting release of said releasable means in response to overload currents, a latch member normally engaging and holding said releasable member, said latch member being mounted on said current responsive means and insulated therefrom by means including `a piece of enameled wire passing through said latch member and` said current responsivemember and having a headed portion at each end thereof.

14. In a circuit breaker having relatively movable contacts and means releasable to effect opening of said contacts, a bimetal element for effecting release of said releasable means, latch means on said bimetal element normally restraining said releasable means, magnetic means energizable by current flowing through said bimetal element for effecting release of said releasable means comprising a magnet yoke mounted for limited movement, an armature mounted on said bimetal element and movable toward said magnet yoke, means rigidly securing said armature on said bimetal element comprising a rivet having a head disposed on the side of said bimetal proximate to said magnet yoke, said rivet having the surface of its shank coated with insulating material to assist in insulating said latch means from said bimetal element and said armature, spring means biasing said magnet yoke to a predetermined positionA to yform an initial air gap with said armature, said magnet yoke having a raised portion on one side forming a seat for said spring means andhaving a recess on the other side for accommodating the head of said rivet to permit close engagement of said armature with said magnet yoke, and lsaid spring means permitting said armature to move a greater distance than said initial air gap.

15. In a circuit breaker having relatively movable contacts and means releasable to elect opening of said contacts, trip means for effect- :ing release of said releasable means in response to overload currents comprising a bimetal element, magnetic means including a magnet yoke supported for limited movement in the direction of thermal bending of said bimetal element to permit maximum bending ofsaid bimetal element without substantial opposition, a spring biasing said magnet yoke to a normal position, an armature mounted on said bimetal element, a latch member mounted on said bimetal element between said bimetal element and said armature, insulating means', for insulating said latch member from said bimetal element and said armature including a rivet having a coating of insulating material thereon and having a projecting head on the side of said bimetal element adjacent said magnet yoke, said magnet yoke having a recess on the side thereof adjacent said bimetal element to accommodate said rivet head and having a raised portion on the side opposite to said recess forming a seat for said spring, and said magnet yoke upon energization of said magnetic means attracting said armature to bend said bimetal element and cause instantaneous release of said releasable means.

16. In a circuit breaker, separable contact means, a movable member for effecting separation of said contact means upon the occurrence of an overload, a bimetal element which bends when heated, a portion rigid with said bimetal element and movable therewith at all times, said portion' when moved to a predetermined position initiating movement of said movable member to effect separation of the contact means, a membei" 'of magnetic material movably mounted on a stationary support adjacent said bimetal element for magnetically bending said bimetal element and moving said portion rigid therewith to said predetermined position, stop means limiting movement of said member of magnetic material toward said bimetal element, and said member of magnetic material being movable relative to its stationary support away iroin said stop means in the direction in which the bimetal element bends when heated.

17. In a circuit breaker, separable contact means, a movable member for effecting separation of said contact means upon the occurrence of an overload, a bimctal element which bends when heated, means connecting said bimetal element in the circuit through the contact means so as to be traversed by current and heated thereby, a portion rigid with said bimetal element and movable therewith at all times, said portion when moved to a predetermned position initiating o movement of said movable member to effect separation of the Contact means, a member of magnetic material movably mounted on a stationary support adjacent said birnetal element, said member of magnetic material being energized by the current ilow through the bimetal element for magnetically bending said bimetal element and moving said portion rigid therewith to said predetermined position upon the flow of a heavy current, stop means limiting movement of said member of magnetic material toward said bimetal element, a spring biasing said member of magnetic material against said stop means, and said member oi magnetic material being movable relative to its stationary support away from said stop means in the direction in which the bimetal element bends when heated and against the bias of said spring.

References Cited in the le of this patent UNTIED STATES PATENTS Number Name Date ,2A-47,652 Jennings Aug. 24, 1948 2,539,567 Best Jan. 30, 195i 2,573,306 Casey Oct. 30, 1951 2,590,663 Walker Mar. 25, 1952 

